Photoconductive compositions and elements and method of preparation

ABSTRACT

Multiphase heterogeneous compositions are formed from an organic dye and electrically insulating polymeric material. A solution of dye and polymer is prepared and subsequently treated, for example, by exposure of a coating thereof to a solvent to form the heterogeneous compositions. These compositions which are useful as photoconductors or electrophotosensitizers are characterized by a radiation absorption maximum that is substantially shifted from the absorption maximum of the dye dissolved in the polymer to form a homogeneous composition. Particularly useful dyes are the pyrylium dyes.

United States Patent William A. Light Rochester, N.Y.

Mar. 4, 1969 Oct. 26, 197 1 Eastman Kodak Company Rochester, N.Y.

Continuation-impart of application Ser. No. 586,820, Oct. 14, 1966, nowabandoned Continuation-impart of application Ser. No. 674,005, Oct. 9,1967, now abandoned.

Inventor Appl. No. Filed Patented Assignee PHOTOCONDUCTIVE COMPOSITIONSAND ELEMENTS AND METHOD OF PREPARATION 26 Claims, No Drawings 11.8. C1..96/l.6, 96/1 R, 252/501, 260/37 PC, 260/345.1, 260/327 B, 106/307 Int.Cl G03g 7/00,

{50] Field oiSearch 96/1 6,1, 1.2, 1.5, l.8;252/.501;260/40, 345.1, 327;106/307 [56] References Cited UNITED STATES PATENTS 3,250,615 5/1966 VanAllan et a1. 96]] 3,397,086 8/1968 Bartfai 117/218 PrimaryExaminer-George F. Lesmes Assistant Examiner-M. B. WittenbergAtrorneys-W. H. J. Kline, .l. R. Frederick and T. Hiatt ABSTRACT:Multiphase heterogeneous compositions are formed from an organic dye andelectrically insulating polymeric material. A solution of dye andpolymer is prepared and subsequently treated, for example, by exposureof a coating thereof to a solvent to form the heterogeneouscompositions. These compositions which are useful as photoconductors orelectrophotosensitizers are characterized by a radiation absorptionmaximum that is substantially shifted from the absorption maximum of thedye dissolved in the polymer to form a homogeneous composition.Particularly useful dyes are the pyrylium dyes.

PHOTOCUNDUCTIVE COMPOSITIONS AND ELEMENTS AND METHOD 01F PREPARATIONThis application is a continuation-in-part of U.S. applications Ser. No.586,820, filed Oct. 14, 1966, now abandoned and Ser. No. 674,005, filedOct. 9, 1967.

This invention relates to electrography and to photoconductivecompositions, elements and structures useful in electrography andparticularly in electrophotography. ln addition, this invention relatesto providing novel electrophotographic compositions together withmethods for their preparation and use.

Electrophotographic imaging processes and techniques have beenextensively described in both the patent and other literature, forexample, U.S. Pat. Nos. 2,221,776; 2,277,013; 2,297,691; 2,357,809;2,551,582; 2,825,814; 2,833,648; 3,220,324; 3,220,831; 3,220,833 andmany others. Generally, these processes have in common the steps ofemploying a nor mally insulating photoconductive element which isprepared to respond to imagewise exposure with electromagnetic radiationby forming a latent electrostatic charge image. A variety of subsequentoperations, now well known in the art, can then be employed to produce apermanent record of the image.

One type of photoconductive insulating structure or element particularlyuseful in electrophotography utilizes a composition containing aphotoconductive insulating material dispersed in a resinous material. Aunitary electrophotographic element is generally produced in amultilayer type of structure by coating a layer of the photoconductivecomposition onto a film support previously overcoated with a layer ofconducting material or the photoconductive composition may be coateddirectly onto a conducting support of metal or other suitable conductingmaterial. Such photoconductive compositions have shown improved speedand/or spectral response, as well as other desired electrophotographiccharacteristics when one or more photosensitizing materials or addendaare incorporated into the photoconductive composition. Typical addendaof this latter type are disclosed in U.S. Pat. Nos. 3,250,615, 3,141,770and 2,987,395. Generally, photosensitizing addenda for photoconductivecompositions are incorporated to effect a change in the sensitivity orspeed of a particular photoconductor system and/or a change in itsspectral response characteristics. Such addenda can enhance thesensitivity of an element to radiation at a particular wavelength or toa broad range of wavelengths where desired. The mechanism of suchsensitization is presently not fully understood. The phenomenon,however, is extremely useful. The importance of such effects isevidenced by the extensive search currently conducted by workers in theart for compositions and compounds which are capable of photosensitizingphotoconductive compositions in the manner described.

Usually the desirability of a change in electrophotographic propertiesis dictated by the end use contemplated for the photoconductive element.For example, in document copying applications the spectralelectrophotographic response of the photoconductor should be capable orreproducing the wide range of colors which are normally encountered insuch use. If the response of the photoconductor falls short of thesedesign criteria, it is highly desirable if the spectral response of thecomposition can be altered by the addition of photosensitizing addendato the composition. Likewise, various applications specifically requireother characteristics such as the ability of the element to accept ahigh surface potential, and exhibit a low dark decay of electricalcharge. 1t is also desirable for the photoconductive element to exhibithigh shoulder speed and high toe speed as measured in an electrical Hand D or characteristic curve, a low residual potential after exposure,and resistance to fatigue. H and D curves as referred to herein areanalogous to the curves first employed by Hurter and Driffield exceptthat voltage or charge on the electrophotographic element is usedinstead of density. Sensitization of many photoconductive compositionsby the addition of certain dyes selected from the large number of dyespresently known has hitherto been widely used to provide for the desiredflexibility in the design of photoconductive elements in particularphotoconductor-containing systems. At the present time,

however, no photosensitizer addenda to photoconductor compositions orelements have been shown to the art which are capable of producing asignificant improvement in substantially all of the aforementioneddesirable characteristics. Conventional dye addenda to photoconductorcompositions have generally shown only a limited capability for overallimprovement in the totality of electrophotographic properties whichcooperate to produce a useful electrophotographic element or structure.The art is still searching for improvements in shoulder and toe speeds,rapid recovery and useful electrophotographic speed from either positiveor negative electrostatic charging. Thus far, dye sensitization alonehas not produced the quality of improvement in photoconductor-containingsystems which might be considered satisfactory for the wide variety ofelectrophotographic applications presently contemplated by workers inthe art.

It is, therefore, an object of this invention to provide the art ofelectrophotography with novel compositions of matter, methods for theirpreparation and elements for their optimum employment.

It is a further object of this invention to substantially remove thelimitations encountered heretofore by novel means using photosensitizingaddenda for organic photoconductive materials in the fieldofelectrophotography. For example, it is an object of this invention toprovide photoconductive compositions and elements having greater speedthan has previously been obtainable with conventional organicphotoconductive compounds or compositions.

It is also an object of this invention to provide novel photoconductivecompositions and elements prepared therefrom which show substantiallyimproved resistance to fatigue and which demonstrate substantiallyincreased speed of recovery between charging and exposure cycles.

It is likewise an object of this invention to provide novelphotoconductive elements having the aforementioned characteristics whichare well suited for use with either positive or negative initialcharging potentials thereby permitting a wide latitude in the selectionand use of image-toning means and compositions as well as providing agreater degree of freedom in the selection ofthe type of image to bereproduced than has previously been possible.

It is still a further object of this invention to provide novelphotoconductive elements containing zinc oxide and having enhancedelectrophotographic properties.

The above and further objects and advantages of this invention willbecome apparent from the following description of the invention.

It has been discovered that many useful photographic sensitizing dyesand mixtures of such dyes, can be combined with electrically insulatingpolymers in solution and treated as described herein to form aseparately identifiable multiphase heterogeneous composition. Theseheterogeneous compositions can be formed as described herein. Thefeature composition thus formed has been found to be useful as either aphotoconductor or as a sensitizer in electrophotographic compositionscontaining other photoconductors.

A solution containing the constituents of the featureelectrophotographic compositions can be coated in the form of a layer ina conventional manner onto a suitable support and the formation ofthecomposition of the invention achieved in situ in the formed layer. Onetechnique for converting a homogeneous coating of dye and polymer to thepresent heterogeneous system is by prolonged contact of the coating tovapors of solvent which is capable of being absorbed in or penetratingthe layers, the dye being caused to migrate and form aggregates in amultiphase system. Usually such vapor exposure is effective to permitformation of a substantial amount of the feature compositions from thedye and polymer in about two minutes at about 70 F. Likewise, inhibitionof solvent removal in an otherwise normal coating operation ofa dopesolution made up of the dye and polymer can form the featurecompositions. Similarly, immersing the homogeneous coating in a solvent,or coating from an original solvent mixture which contains a highboiling solvent which persists in the coating during drying, are amongother methods of forming the feature compositions. Another suitabletechnique for forming the present heterogeneous compositions involveshigh speed shearing ofa solution of dye and polymer in accordance withthe procedure described in copending Gramza application Ser. No.674,006, filed Oct. 9, 1967, now abandoned.

Observable heterogeneous structure in the present photoconductive layersis indicative of the presence of the feature compositions. The presenceof such compositions in the layer permits the layer to produce thehereinafter enumerated improved properties when used as a photoconductoror as a photosensitizing addendum for other photoconductors. The featurecompositions when formed in situ in the layer generally have anidentifiable heterogeneous appearance when viewed under at least 2500Xmagnification, although such compositions may appear to be substantiallyoptically clear to the naked eye in the absence of magnification. Inother compositions of the invention there is a macroscopicheterogeneity. Suitably, the dye-containing aggregate in thediscontinuous phase in predominantly in the size range of about 0.01 to25 microns. However, it should be noted that when the heterogeneouscompositions of the invention are used to sensitize a particulatephotoconductor, such as zinc oxide, another discontinuous phase will bepresent which may not fall within this size range.

in general, the present heterogeneous compositions are two phase organicsolids containing dye and polymer. The polymer forms an amorphous matrixor continuous phase which contains a discrete discontinuous phase asdistinguished from a solution. The discontinuous phase contains asignificant portion of the dye present and generally a predominantportion of the dye present is in the discontinuous phase. The dye in thediscontinuous phase can be considered as being in particulate form;however, that phase need not be comprised wholly of dye. It is believedthat in some instances the discontinuous phase may be comprised ofacocrystalline complex of dye and polymer. However, it is also believedthat all of the aggregates which can be formed in accordance with thisinvention are not necessarily comprised of both dye and polymer.Preferably, substantially all of the dye present in the system is in thediscontinuous phase. When the present compositions are used inconjunction with an organic photoconductor, the resultantphotoconductive composition generally contains only two phases as thephotoconductor usually forms a solid solution with the continuouspolymer phase. On the other hand, when the present multiphasecompositions are used in conjunction with a particulate photoconductor,three phases may be present. In such a case, there would be a continuouspolymer phase, a discontinuous phase containing dye as discussed aboveand another discontinuous phase comprised of the particulatephotoconductor. Of course, the present multiphase compositions may alsocontain additional discontinuous phases.

The feature compositions of this invention have shown many usefulproperties in the electrophotographic art. Electrophotographic elementsmade with layers containing this new substance alone or together withother photoconductive compounds and compositions are broadly improved.The feature compositions of this invention can be specificallyidentified by their effect as a photoconductive material per se or uponother photoconductive materials as sensitizers therefor. A particularlydistinctive property characteristic of electrophotographic elementshaving coated thereon many of the compositions of the invention is anincreased photosensitivity irrespective of the polarity of surfacecharge placed on the photoconductive element. Such photoconductiveelements exhibit high photosensitivity and photoconductivity as well asgood regeneration. The observed tendency of elements containing thematerial of this invention to recover very rapidly after charging andexposure is important in continuous or cyclic electrophotographicapplications. When a feature composition of the invention is present inan electrophotographic element, the element has an improved ability torepeatedly accept a high surface potential after completion of acharge-expose-develop cycle. Such elements can, therefore, be furthercharacterized by their resistance to the kind of electrical fatiguewhich is normally characteristic ofphotoconductor-containing elementsand which prevents rapid reuse of such elements.

The prior art photoconductive layers can be prepared in a wide varietyof ways. Typically, a solution comprising a photoconductor, afilm-forming hydrophobic binder and a sensitizing dye can be prepared asshown in U.S. Pat. No. 3,141,770 and cast or coated in the manner taughttherein, for example, in the form of a layer onto a suitably preparedconducting support material. A layer prepared in this manner absorbsradiation over a particular wavelength region charac teristic of the dyeused and appears substantially homogeneous under 2500X magnification.The electrophotographic properties of these prior art photoconductivelayers are adequate for the preparation of a useful image when charged,exposed imagewise and developed in the conventional manner. However,according to this invention, a significant improvement in many of theelectrophotographic properties presently characteristic of these typesof materials, particularly a speed increase, is provided by theformation of the feature nonhomogeneous multiphase compositions of thisinvention. The wavelength of the radiation absorption maximumcharacteristic of the heterogeneous compositions is substantiallyshifted from the wavelength of the radiation absorption maximum of thesubstantially homogeneous untreated dyepolymer solid solution. The newabsorption maximum characteristic of the aggregates of this invention isnot necessarily an overall maximum for the system as this will dependupon the relative amount of dye in the aggregate. Such an absorptionmaximum shift in the formation of the present multiphase heterogeneoussystems is generally of the magnitude of at least about 10 mp" Ifmixtures of dyes are used, one dye may cause an absorption maximum shiftto a longer wavelength and another dye cause an absorption maximum shiftto a shorter wavelength. In such cases the formation of the presentheterogeneous compositions can be more easily identified by viewingunder magnification. To prepare such an improved element aphotoconductive layer prepared as described above can be exposed to thevapor of an organic solvent. For example, after about two minutes atroom temperature or about 70 F. this treatment produces changes in thelayer. The color of the layer during treatment changes, e.g. from a deepblue to a shade of red, and absorbs radiation in a wavelength regiondifferent than the original material. When the photoconductive layer isremoved from the solvent vapor and viewed under magnification, the layercontaining the feature composition has a two phase heterogeneousappearance.

A photoconductive layer of the invention transformed as above, inaddition to having undergone physical appearance changes, has alsoundergone a conversion which imparts to the layer the novel propertiesdescribed herein such as an increased electrophotographic speed,sometimes regardless of the polarity of the original electrostaticcharge. Sometimes the dark conductivity of such transformed material isalso lowered, and the layer can be repeatedly charged and exposed withno apparent electrical fatigue. Likewise, such feature photoconductivelayers do not have a memory or retain spurious images when subsequentlycharged and exposed. The present photoconductive material can be rapidlycharged and its charge stability is high when subjected to high humidityor repeated exposure and development.

Particularly useful dyes in the present invention are pyrylium dyes,including pyrylium, thiapyrylium and selenapyrylium dye salts, which arecapable of forming sensitizing and photoconductive compositions of thisinvention can be represented by the following general formula:

wherein R", R,,, R, R", and R" can each represent (a) a hydrogen atom;(b) an alkyl group typically having from 1 to carbon atoms, such asmethyl, ethyl, propyl, isopropyl butyl, tertiary butyl, amyl, isoamyl,hexyl, octyl, nonyl, dodecyl, etc, (0) alkoxy groups like methoxy,ethoxy, propoxy, butoxy, amyloxy, hexoxy, octoxy, and the like; and (d)aryl groups including substituted aryl groups such as phenyl,4-diphenyl, a1-

kylphenyls as 4-ethylphenyl, 4-propylphenyl, and the like, 211-koxyphenyls as 4-ethoxyphenyl, 4-methoxyphenyl, 4-amyloxyphenyl,2-hexoxypheny1, Z-methoxyphenyl, 3,4-dimethox-,

yphenyl, and the like, B-hydroxy alkoxyphenyls as Z-hydroxyethoxyphenyl,3-hydroxyethoxyphenyl, and the like, 4-

hydroxyphenyl, halophenyls as 2,4-dichlorophenyl, 3,4- dibromophenyl,4-chlorophenyl, 2,4-dichlorophenyl, and the like, azidophenyl,nitrophenyl, aminophenyls as 4- diethylaminophenyl,4-dimethylaminophenyl and the like, napthyl; and vinyl substituted arylgroups such as styryl, methoxystyryl, diethoxystyryl,dimethylaminostyryl, l-butyl- 4-p-dimethylaminophenyll ,3-butadienyl,,B-ethyl-4- dimethylaminostyryl, and the like; and where X is a sulfur,oxygen or selenium atom, and Zis an anionic function, including suchanions as perchlorate, fluoroborate iodide, chloride, bromide, sulfate,periodate, p toluenesulfonate, and the like. In

addition, the pair R" and R as well as the pair R" and R" cantogether bethe necessary atoms to be complete an aryl ring fused to the pyryliumnucleus.

Typical pyrylium dyes for use in the present invention are listed intable 1.

TABLE 1 Compound Number Name of Compound l2MM-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6- phcnylthiapyryliumperchlorate l3 4-(4-dimethylaminophenyl)-2 (4-rnethoxyphenyl)-6-(Lmethylphenyl)pyrylium perchlorate l4 4-(4-diphenylaminophenyl)-2,6-

diphenylthiapyrylium perchlorate l5 2,4,64riphenylpyrylium perchlorateperchlorate l7 4-( 2,4-dichlorophenyl)-2,6-diphenylpyrylium perchloratel8 4-( 3,4-dichlurophenyl)-2,6diphenylpyrylium perchlorate l92,6-bis(4-methoxyphenyl)-4-phcnylpyrylium perchlorate 206(4-methoxyphenyl )2.4-diphenylpyrylium perchlorate 212-(3,4-dichlorophenyll-4-(4-methoxyphenyly6- phenylpyrylium perchlorate22 4-(4-amyloxyphenyl)-2,6-bis(4'ethylphenyl )pyrylium perchloratemethoxyphenyhpyrylium perchlorate Z4 2,4,6-triphenylpyryliumfluoroborate Ill 2,6-bis(4-ethylphenyl)-4-(4- methoxyphenyl)pyryliumperchlorate 2.6'bis(4-ethylphenyl)-4-(4- methoxyphenyhpyryliumfluoroborate 6-(3.4diethoxystyryl)-2.4-diphenylpyrylium perchlorate6-(3,4-dicthoxy-fi-amylstyryl)-2,4-diphenylpyrylium fluoroborate6-(4-climethylamino-B-ethylstyryl)-Z 4- diphenylpyrylium fluorohorate6-( l-n-amyl-4-p-dimethylaminophenyl 1,3

butadienyl)2.4-diphenylpyrylium fluoroborate6-(4-dimethylaminostyryl)-2,4-diphenylpyrylium fluoroborate6-(or-ethyl-flfi-dimethyleminopheniyl vinylene)-2.4-

diphenylpyrylium fluoroborate 6-( l-butyl-4-p-dimethylaminophenyl-l,3-

butadienyl)-2,4-diphenylpyryliurn fluoroborate6-(4-dimethylaminostyryl)-2.4-diphenylpyryliurr\ perchlorate6-[fi.fl-bis(4 -dimethylaminophenyI|)vinylene]-2.4-

diphenylpyrylium perchlorate2,6-bis(4-dimethylaminostyryl)--phenylpyrylium perchlorate6-(fimethyl-4-dimethylaminostyryl)-2.4-

diphenylpyrylium fluoroborate 64 l ethyl-4-p-dimethylaminophenyl-l,J-butadienyl- 2,4 diphenylpyrylium fluoroborate6-[fi,fl-bis(4-dimethylaminophenylJvinylene]-2.4-

diphenylpyrylium fluoroborate 6-( l-methyl-4p-dirnethylaminophenyl-l ,3-

butaclienyl)-2,4-diphenylpyrylium fluoroborate4-(4-dimethylarninophenyl)-2,6-diphenylpyrylium perchlorate2,6bis(4-ethylphenyl)-4- henylpyrylium perchlorate 26-bis(4-ethylphenyl)4-methoxyphenylthiapyryliurn fluoroboratc2.4,6-triphenylthiapyrylium perchlorate4-(4-methoxyphenyl)-2.fi-diphenylthiapyrylium erchlorate 6(4-methoxvphenylr2,d-diphenylthiapyrylium perchlorate2,6bis(4-methoxyphenyl)-4-phenylthiapyrylium perchlorate4-(2,4-dichlorophenyl)-2,6-diphenylthiapyrylium perchlorate2,4,6-tris(4-methoxyphenyl)thiapyrylium perchlorate2,6-bis(4-ethylphenyl)-4-phenylthiapyrylium perchlorate4-(4-amyloxyphenyl)-2.6-bis(4- ethylphenyhthiapyrylium perchlorate6-t4-dimethylaminostyryl) Z,4-diph-enylthiapyrylium perchlorate2.4,fi-triphcnylthiapyrylium l'luoroborate 2,4.6'triphenylthiapyryliumsulfate 4-( 4-methoxyphenyl b-Z,6-diphcnylthiapyrylium l'luorohorate 2.46 triphenylth|apyrylium chloride 2-(4-amyloxyphenyl)-4.G-diphenylthiapyrylium fluoroborate4-(4-amyloxyphcr|yl)-Z,6-his(4 methoxyphenyl)thiapyrylium perchlorate2.6-bis(4-ethylphenyli444- methoxyphenyl)thiapyrylium perchlorate4-anisyl 2,6-bis(4-n-amyloxyphenylltthiapyrylium chloride 2[B,fl-bis(4-dimethylaminophenyl)winylene]4,6-

diphenylthiapyrylium perchlorate 6-(dethylA-dirnerhylaminostyryl)-2.4-di henylthiapyrylium perchlorate2-(3,4.4]iethoxystyryl)-4,6-diphenylthiapyrylium perchlorateZ,4,6-trianisylthiapyrylium perchlorate 2,6-bist4-ethylphenyl)-4-(4-methoxyphenyl)thiapyrylium chloride6[B,,B-bis(4-dimcthylaminophenyl)vinylene]-2 4-bis(4-ethylphenyl)pyrylium perchlorate Z 6-bis(4-amyloxyphenyl)-4(4-methoxyphenyl)thiapyrylium perchlorate 2 (4ethylpheny|)-4.6-diphenylthiayrylium perchlorate 2,6'diphenyl-4-(4-methoxyphenyl )thiapyryliumperchlorate 2,6-diphenyl-4-(4-methoxyphenyl)thiapyrylium fluoroborate2,6-bis(4ethylphenyl-4-(4-namyloxyphenyl)thiapyrylium perchlorate2,6-bis(4-methoxyphenyl) 4-(4-namyloxyphenyl)thia yrylium perchlorate 762.4.6-tris(4-methoxyphenyl)thiapyrylium fluoroboratc 77 24-diphenyl-6-(3 4-diethoxystyryl)pyrylium perchlorate 784-(-dimethylaminophenyU-Z- phenylbenzotb)selenapyrylium perchlorate 792-(2,4-dimethoxyphenyl)-4-(4- dimerhylaminohenyl)-benzo(b)selenapyrylium perchlorate 80 4(4-dimcthylaminophenyl)-2,6-

diphenylselenapyrylium perchlorate 8l4-(4-dimcthylaminophenyl)-2-(4-ethoxyphenyl)-6- phenylselenapyryliumperchlorate 82 4-[4-bis(2-chloroethyl)aminophenyl1-2.6-

diphenylselenapyrylium perchlorate 834-(4-dimethylaminophenyl)-2,6-bis(4-ethylphenyl)- selenapyryliumperchlorate 84 4-(4-dimethylamino-2-methylphenyl)-2,6- X5diphenylselenapyrylium perchlorate 8S3-(4-dimethylaminophenyl)naphtho(2.l-

b)selenapyrylium perchlorate 86 4-(4-dimethylaminosryryl)-2-(4-methoxyphenyl)benzo(b)selenapyrylium perchlorate 872.6-di(4-diethylaminophenyl)-4- phenylselenapyrylium perchlorate 884-(4-dimethylaminophcnyl)-2-(4-ethoxyphenyl)-6- phenylthiapyryliumfluoroborate Preferred pyrylium dyes used informing the featureaggregates are pyrylium dye salts having the formula:

Iii-K R I Z- a wherein:

R and R can each be phenyl radicals, including substituted phenylradicals having at least one substituent chosen from alkyl radicals offrom I to 6 carbon atoms and alkoxy radicals having from 1 to 6 carbonatoms;

R can be an alkylamino-substituted phenyl radical having from 1 to 6carbon atoms in the alkyl moiety including dialkylamino-substituted andhalogenated alkylamino-substituted phenyl radicals;

X can be an oxygen or a sulfur atom; and Z is the same above.

While the pyrylium dyes are preferred in preparing the present two-phaseheterogeneous systems, other photographic spectral sensitizing dyes thatactivate light exposed areas of photographic compositions can beutilized in the electrically insulating polymer of the present system,such as the J-aggregated dyes disclosed in copending Gilman andHeseltine U.S application Ser. No. 804,267, cofiled herewith andentitled PHOTOCONDUCTIVE COMPOSITIONS AND ELE- MENTS, including.I-aggregates of cyanine, merocyanine and 5 styryl dyes such asanhydro-Lethyll '-sulfobutyl-2,2'-cyanine hydroxide,

2-( 5 ,5 -dicyano-2,4-pentenylidene )-3-ethyl- 380 to about 1,000 my.

Electrically insulating filmforming polymers suitable for the formationof clectrophotographic compositions containing the feature aggregates ofthis invention include polycarbonates and polythiocarbonates, polyvinylethers, polyesters, polya-olefins, phenolic resins, and the likeMixtures of such polymers can also be utilized. Such polymers includethose which function in the formation of the aggregates of thisinvention as well as functioning as binders for the sensitizer andphotoconductor. Typical polymeric materials from these classes are setout in table 2.

TABLE 2 Number Polymeric Materials l polystyrene 2 polyvinyltoluene 3polyvinylanisole 4 polychlorostyrene 5 polya-methylstyrene 6polyacenaphthalene 7 poly(vinyl isobutyl ether) 8 poly(vinyl cinnamatc)9 poly(vinyl benzoate) l0 poly(vinyl naphthoate) l l polyvinyl carbazolel2 poly(vinylene carbonate) l3 polyvinyl pyridine l4 poly(vinyl acetal)l5 poly(vinyl butyral) l6 poly(ethyl methacrylate) l7 poly(butylmethacrylate) l8 poly(styrene-co-butadienc) l9 poly(styrene-co-methylmethacrylate) 20 poly(styrene-co-ethyl ucrylatc) 2|poly(styrene-co-acrylonitrile) 22 poly(vinyl chloride-co-vinyl acetate)23 poly(vinylidene chloride-co-vinyl acetate) 24poly(4,4-isopropylidenediphenyl-co-4,4'-

isopropylidenedicyclohexyl carbonate 25 poly[4,4'-isopropylidendbi$(2.6

dibrOmophenyUCarbonate] 26poly(4,4'-isopropylidenebis(2.6-dichlorophenyl)- carbonate] 27poly[4,4'-isopropylidenebis(2.6-

dimethylphenyl)carbonate] 28 poly(4,4'-isopropylidenediphenyl-co-1.4-

cyclohexyldimethyl carbonate) 29 poly(4 4'-isopropylidenediphenylterephthalatc-coisophthalatc) 30 poly(3,3'-ethylenedioxyphenylthiocarbonate) 3l poly[4.4'-isopropylidenediphenylcarbonate-coterephthalatc) 32 poly(4,4'-isopropylidenediphenylcarbonate) 33 poly(4,4'-isopropylidenediphenyl thiocarbonate) l4poly(2,2-butancbis-4-phenyl carbonate) 3S poly(44'-is0propylidcnediphenyl carbonate-block ethylene oxide) 36poly(4,4'-isopropylidenediphenyl carbonate-block tetramethyleneoxide) 37poly[4,4'-isopropylidcnebis(2- methylphenyUcarbonale] 38poly(4.4-isopropyliclenediphenyl-co-l .4-phcnylene carbonate) 39poly(4.4'-isopro ylidcnediphenyl-co-l.3-phenylcne carbonat 40poly(4,4-isopropylidenediphenyl-co-4.4'-diphenyl carbonate 4]poly(4.4'-isopropylidenediphenyl-co-4.4'-

oxydiphcnyl carbonate) 42 poly(4.4'-isopropylidenediphenyl-co-4Acarbonyldiphenyl carbonate) 43 poly(4 4'-isopropylidencdiphcnyl-co-4.4

elhylcnediphenyl carbonate) 44 poly[4,4-methylenebis(Z-methylphenyl)carbonate] 45 poly[ l ,l-(p-bromophenylethane)bis(4-phenyl)carbonate] 46 poly[ 4,4 isopropylidenediphenyl-cmsull'onyl bis(4-phenyl)carbonate] 47 poly[ l ,l-cyclohexane bis(4-phenyl)carbonate] 48poly(4,4'-isopropylidenediphenoxydimethylsilane) 49poly[4.4'-isopropylidene bis(2-chlorophenyl carbonate] S0poly[a.a.u'.a-tetramethyl-p-xlcne his(4-phenyl carbonate)] 5]poly(hexnfluoroisopropylidenedi-d-phenyl carbonate) 52poly(dichlorotetrafluoroisopropylidenedi-l-phenyl carbonate) 53 poly(44-isopropylidenediphenyl 4,4-

isopropylidcne-dibenzoate) 54 poly(4.4'-isopropylidcnedibenzyl 4.4

isopropylidene-dibenzoate) 55 poly(4.4'-isopropylidencdi-l-naphthylcarbonate) $6 poly[4.4-isopropylidene bis(phenoxy-4-phenyl sulfonateH 57acetophenone formaldehyde resin 58 poly[4,4-isopropylidenebis(phenoxyethyl)-coethylene terephthalate] S9 phenol-formaldehyde resin60 polyvinyl acetophenone 6i chlorinated polypropylene 62 chlorinatedpolyethylene 63 poly(2,6-dimethylphenylene oxide) 64poly(ncopentyl-2,6-naphthalenedicarboxylate) 65 poly(ethyleneterephlhalate-co-isophthalate) 66 poly( l,4-phenylene-co'1,3-phenylenesuccinate) 67 poly(4,4'-isopropylidenediphenyl phenylphosphonate) 68polylm-phenylcarboxylate) 69 poly( l ,4-cyclohexanedimethylterephthalate-co' isophthalate) 70 poly(tetramethylene succinate) 71poly(phenolphthalein carbonate) 72 poly(4-chloro- 1,3-phenylenecarbonate) 73 poly(2-methyl-l ,3-phenylene carbonate) 74 poly(l,l-bi-2-naphthyl thiocarbonate) 75 poly(diphenylmethane bis-4 phenylcarbonate) 76 poly[2,2-(3-methylbutanc)bis-4-phenyl carbonate] 77poly[2,2-l3,3-dimethylbutane)bis-4-phenyl carbonate] 78 polyl,l-|1-(l-naphtliylethylidene)lbis 4-phenyl carbonate 79poly[2,2-(4-methylpentane)bis-4-phenyl carbonate] 80poly[4,4'-(2-norbornylidcne)diphenyl carbonate]poly[4,4'-(hcxahydro-4,7-methanoindan-5- lidene)diphenyl carbonate]Especially useful polymers for forming the present heterogeneouscompositions are compounds number 28, 30-47, 49, 51, 53, 54 and 76-8l aslisted in table 2 above.

Included among the preferred polymers used for preparing the two-phaseheterogeneous compositions of the invention, including copolymers, arethose linear polymers having the following recurring unit:

wherein:

R and R when taken separately, can each be a hydrogen atom, an alkylradical such as methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl,pentyl, hexyl, heptyl, octyl, nonyl, decyl and the like includingsubstituted alkyl radicals such as trifluoromethyl, etc. and an arylradical such as phenyl and naphthyl including substituted aryl radicalshaving such substituents as a halogen, alkyl radicals of from 1 to 5carbon atoms, etc.; and R, and R when taken together, can represent thecarbon atoms necessary to form a cyclic hydrocarbon radical includingcycloalkanes such as hexyl and polycycloalkanes such as norbornyl, thetotal number of carbon atoms in R and R being up to 19;

R and R, can each be hydrogen, an alkyl radical of from 1 to 5 carbonatoms or a halogen such as chloro, bromo, iodo, etc, and

R is a divalent radical selected from the following:

Among the hydrophobic carbonate polymers particularly useful inaccordance with this invention are polymers comprised of the followingrecurring unit:

wherein:

each R is a phenylene radical including halo substituted phenyleneradicals and alkyl substituted phenylene radicals; and R, and R aredescribed above. Such compositions are disclosed, for example, in US,Pat. Nos, 3,028,365 and 3,317,466. Preferably polycarbonates containingan alky- .lidene diarylene moiety in the recurring unit such as thoseprepared with Bisphenol A and including polymeric products of esterexchange between diphenylcarbonate and 2,2-bis(4- hydroxyphenyl)-propaneare used in the practice of this invention Such compositions aredisclosed in the following US. Pat Nos. 2,999,750; 3,038,874; 3,038,879;3,038,880; 3,106,544; 3,106,545; 3,106,546; and published AustralianPat. Specification No. 195 75/56. A wide range of film-formingpolycarbonate resins are useful, particularly completely satisfactoryresults are obtained when using commercial polymeric materials which arecharacterized by an inherent viscosity of about 0.5 to 0.6. In addition,a high molecular weight material such as a high molecular weightBisphenol A polycarbonate can be very useful. Preferably, such highmolecular weight materials have an inherent viscosity of greater thanabout 1 as measured in 1,2-dichloroethane at a concentration of 0.25 g./ml. and a temperature of about 25 C. The use of high molecular weightpolycarbonate, for example, facilitates the formation of aggregatecompositions having a higher dye concentration which results inincreased speeds.

Liquids useful for treating polymer-dye coatings to form the aggregateor heterogeneous compositions of the invention can include water, and anumber of organic solvents such as aromatic hydrocarbons, for example,benzene and toluene, ketones such as acetone and ethylmethyl ketone,halogenated hydrocarbons such as methylene chloride and alcohols likemethyl, ethyl, and benzyl alcohol, as well as mixtures of such solvents.

The present heterogeneous compositions are electrically insulating inthe dark such that they will retain in the dark an electrostatic chargeapplied to the surface thereof. in addition, as mentioned above, thepresent compositions are also photoconductive. This term has referenceto the ability of such compositions to lose a retained surface charge inproportion to the intensity of incident actinic radiation. in general,the term photoconductive" as used to describe the present heterogeneouscompositions means that the amount of incident radiation energy inmeter-candle-seconds required to cause a l00-vo1t reduction in retainedsurface potential is not greater than about 200 meter-candle-seconds.

The heterogeneous compositions of this invention are typically coated asa photoconductor or as a sensitizer onto a conventional conductingsupport such as paper (at a relative humidity above '20 percent)including paper made more conductive by various coating and/or sizingtechniques or carrying a conducting layer such as a conducting metalfoil, a layer con taining a semiconductor dispersed in a resin, aconducting layer containing the sodium salt of a carboxyester lactone ofmaleic anhydride and a vinyl acetate polymer such as disclosed in US.Pat. Nos. 3,007,901 and 3,262,806, a thin film of vacuum depositednickel, aluminum, silver, chromium, etc., a conducting layer asdescribed in U.S, Pat. No. 3,245,833, such as cuprous iodide, and likekinds of conducting materials. Such conducting materials can be coatedin any well known manner such as doctor-blade coating, swirling,dip-coating, spraying, and the like. Other supports, including suchphotographic film bases as poly(ethylene terephthalate), polystyrene,polycarbonate, cellulose acetate, etc., bearing the above conductinglayers can also be used. The conducting layer can be overcoated with athin layer of insulating material selected for its adhesive andelectrical properties before application of a photoconducting layer.Where desired, however, the photoconducting layer can be coated directlyon the conducting layer where conditions permit to produce the unusualbenefits described herein.

When the present multiphase compositions of the invention are used asphotoconductive compositions, useful results are obtained by using thedescribed dyes in amounts of from about one to about 50 percent byweight of the coating composition.

When the present multiphase compositions are used as sensitizers forphotoconductive coatings, useful results are obtained by using thedescribed dyes in amounts of about 0.001

to about 30 percent by weight of the photoconductive coatingcomposition, although the amount used can be widely varied. The upperlimit in the amount of photoconductive composition present in asensitized layer is determined as a matter of individual choice and thetotal amount of any photoconductor used will vary widely depending onthe material selected, the electrophotographic response desired, theproposed structure of the photoconductive element and the mechanicalproperties described in the element. Lesser amounts of the presentfeature compositions can be utilized as sensitizing amounts to increasethe speed sensitivity of other photoconductors than amounts that wouldbe used if the feature material were the only photoconductor present.

Coating thicknesses of a photoconductive composition containing thefeature material of the invention can vary widely. More generally, a wetcoating in the range from about 0.005 inch to about 0.05 inch on asuitable support material is used in the practice of the invention. Thepreferred range of wet coating thickness was found to be in the rangefrom about 0.002 inch to about 0.030 inch.

The present invention can readily be used for enhancing the sensitivityand extending the spectral range of sensitivity of a variety of organicphotoconductors and inorganic photoconductors including both nand P-typephotoconductors. For example, the present invention can be used inconnection with organic, including organometallic, photoconductingmaterials which have little or substantially no persistence ofphotoconductivity. Representative organometallic compounds are theorganic derivatives of Group Illa, [V0, and Va metals such as thosehaving at least one amino-aryl group attached to the metal atom.Exemplary organometallic compounds are thetriphenyl-p-dialkylaminophenyl derivatives of silicon, germanium, tinand lead, the tri-p-dialkylaminophenyl derivatives of arsenic, antimony,phosphorus, bismuth boron, aluminum, gallium, thallium and indium.Useful photoconductors of this type are described in copending Goldmanand Johnsom U.S. Pat. application Ser. No. 650,664, filed July 3, 1967and Johnsom application Ser.No. 755,711, filed Aug. 27, 1968.

An especially useful class of organic photoconductors is referred toherein as organic amine photoconductors. Such organic photoconductorshave as a common structural feature at least one amino group. Usefulorganic photoconductors which can be spectrally sensitized in accordancewith this invention include, therefore, arylamine compounds comprising(1) diarylamines such as diphenylamine, dinaphthylamine,N,N-diphenylbenzidine,N-phenyl-l-naphthylamine,N-phenyl-2-napthylamine,N,N'-diphenyl-p-phenylenediamine,2-carboxy-5-chloro-4'-methoxydiphenylamine, p-anilinophenol,N,N'-di-2-naphthyl-p-phenylenediamine, those described in Fox U.S. Pat.3,240,597, issued Mar. 15, 1966, and the like, and (2) triarylaminesincluding (a) nonpolymeric triarylamines, such as triphenylamine,N,N,N'-N'-tetraphenylm-phenylenediamine, 4-acetyltriphenylamine,4-hexanoyltriphenylamine, 4-lauroyltriphenylamine,4-hexyltriphenylamine, 4-dodecyltriphenylamine,4,4-bis(diphenylamino)benzil, 4,4-bis(diphenylamino)benzophenone and thelike, and (b) polymeric triarylamines such as poly[N,4"]polysebacyltriphenylamine, polydecamethylenetriphenylamine,polyN-(4-vinylphenyl)diphenylamine, polyN-(vinylphenyl)- a,a-dinaphthylamine and the like. Other useful amine'type photoconductorsare disclosed in U.S. Pat. No. 3,180,730, issued Apr.27, 1965.

Useful photoconductive substances capable of being sensitized inaccordance with this invention are disclosed in Fox U.S. Pat. No.3,265,496, issued Aug. 9, 1966, and include those represented by thefollowing general formula:

wherein T represents a mononuclear or polynuclear divalent aromaticradical, either fused or linear (e.g., phenyl, naphthyl, biphenyl,binaphthyl, etc.), or a substituted divalent aromatic radical of thesetypes wherein said substituent can comprise a member such as an acylgroup having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl,butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms(e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, pentoxy,etc.), or a nitro group; M represents a mononuclear or polynuclearmonovalent aromatic radical, either fused or linear (e.g., phenyl,naphthyl, biphenyl, etc.), or a substituted monovalent aromatic radicalwherein said substituent can comprise a member, such as an acyl grouphaving from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl,etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g.,methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 toabout 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitrogroup; O can represent a hydrogen atom, a halogen atom or an aromaticamino group, such as MNI-I-; b represents an integer from 1 to about 12;and, R represents a hydrogen atom, a mononuclear or polynuclear aromaticradical, either fused or linear (e.g., phenyl, naphthyl, biphenyl,etc.), a substituted aromatic radical wherein said substituent comprisesan alkyl group, an alkoxy group, an acyl group, or a nitro group, or apoly(4-vinylphenyl) group which is bonded to the nitrogen atom by acarbon atom of the phenyl group.

Polyarylalkane photoconductors are particularly useful in producing thepresent invention. Such photoconductors are described in U.S. Pat. No.3,274,000, French Pat, No. 1,383,461 and in copending application ofSeus and Goldman titled PHOTOCONDUCTIVE ELEMENTS CONTAINING ORGANICPHOTOCONDUCTORS, Ser. No. 627,857, filed Apr. 3, 1967, now U.S. Pat. No.3,542,544. These photoconductors include leuco bases of diaryl ortriaryl methane dye salts, l,l,l-triarylalkanes wherein the alkanemoiety has at least two carbon atoms and tetraarylmethanes, there beingsubstituted an amine group on at least one of the aryl groups attachedto the alkane and methane moieties of the latter two classes ofphotoconductors which are nonleuco base materials.

Preferred polyarylalkane represented by the formula:

photoconductors can be wherein each of D, E and G is an aryl group and.l is a hydrogen atom, an alkyl group, or an aryl group, at least one ofD, E and G containing an amino substituent. The aryl groups attached tothe central carbon atom are preferably phenyl groups, although naphthylgroups can also be used. Such aryl groups can contain such substituentsas alkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy,halogen, etc., in the ortho, meta orpara positions, orthosubstitutedphenyl being preferred. The aryl groups can also be joined together orcyclized to form a fluorene moiety. for example. The amino substituentcan be represented by the formula wherein each L can be an alkyl grouptypically having 1 to 8 carbon atoms, a hydrogen atom, an aryl group, ortogether the necessary atoms to form a heterocyclic amino grouptypically having 5 to 6 atoms in the ring such as morpholino, pyridyl,pyrryl, etc. At least one of D, E, and G is preferablyp-dialkylaminophenyl group. When .1 is an alkyl group, such an alkylgroup more generally has 1 to 7 carbon atoms.

Representative useful polyarylalkane photoconductors ln- E4 clude thecompounds listed in table 3.

Inventor US. Patent No. TABLE3 Hoegl et al. 3.037. Sues et al. 3,041.]65Schlesinger 3,066,023 Compound Bethe 3.072.479 Number Name of CompoundKlupfel et al. 3,047,095 N eta]. 3,ll2,l97 Cassiers et al. 3. l 33,022 I4,4-benzylidene-bis(N,N-diethyl-m-toluidine) Schlesinger 3M4633 24',4"-diaminoA-dimethylaminoQ'.2"- Noe a! a1 3 I 22435dimethyltriphenylmethane sues a a1 3J27'266 34',4"-bis(diethylamino)-2.6dichloro-2,2" scmesinger 31303146dimethyltriphenylmethane 5 Cassie 3 13| 060 4 4.4"-is-(diethylamino)-2'.2"' Schlesinger 3l3933gdimethyldiphenylnaphthylmethane Schlesinger 3.1395539 52'.2"-climethyl-4,4',4"-tris(dimethylamino- Cassius 3.140346)triphenylmethane Davis at al. 3J4 l .770 64',4"-bis(diethylarnino)-4-dimethylamino-2',2"- g 3J48'932dimethyltriphenylmethane 2O Cassiers 3.l55.503 74',4"-bis(diethylamino)-2-chloro2'.2"-dimethyl-4- Cassius 7dimethylaminotriphenylmethane Tomanek 3,l6l.505 8 4,4--bis(diethylaminol 4-dimethylamino-2,2',2"- Schlesinger 3J63530 trimethyltriphenylmethaneS hl i 3, l 63,53l 9 4',4''-bis(dimethylamino-2-chlori:J-2'.2''Schlesinger 3.1 3.53 dimethyltriphcnylmethane 2 H l 3,|69,06() l0 4',4"bis(dimethylamino)-2',2"-dimethyl 4- 5 smmpf 3 I 74854methoxytriphenylmethane Klupfel et al. 3.l80.729 llbis(4-diethylamino)-l,IJ-triphenylethane Kl f l 8 3|, 3 |80 730 l2bis(4-diethylamino)tetraphenylmethane Nwgebauer 3339347 13 4',4"-bis(bcnzylethylamino)-2'.2"- Neugebauer 3.20 .3 6dimethyltriphenylmcthane F 3,240,597 l4 4'. "-bis(d y am Schlesinger3,257.202

diethoxytriphenylmelhane S er 1, 3 357 203 l5 4,4-bis(dimethylamin0)-l.l .l-triphenylethane s cl 3,257,203 l6 l-(4N.N-dimethylaminophcnyh-l,l-diphenylcthane p 3261496 I?4-dimethylaminotetraphenylmethane K h 3361497 l84-diethylaminctetraphenylmethane N e I, 3,274.000

The composition of the present invention can be employed inphotoconductive elements useful in any of the well known Another classof photoconductors useful in this invention elcctrophotographicprocesses which require photoconducare the 4-diarylamino-substitutedchalcones. Typical comtive layers. One such process 18 the xerographlcprocess. In a pounds of this type are low molecular weight nonpolymericprocess of this type, an electrophotographlc element held in ketoneshaving the general formula: the dark is given a blanket electrostaticcharge by placing it i under a corona discharge to give a uniform chargeto the sur- 0 face of the photoconductive layer. This charge is retainedby 3 L the layer owing to the substantial dark insulating property ofthe la er, i.e., the low conductivit of the la er in the dark. R, Y y yThe electrostatic charge formed on the surface of the photoconductivelayer is then selectively dissipated from the wherein R, and R are eachphenyl radicals including subsurface of the layer by imagewise exposureto light by means stituted phenyl radicals and particularly when R is aphenyl ofa conventional exposure operation such as, for example, byradical having the formula: a contact-printing technique, or by lensprojection of an image, and the like, to thereby form a latentelectrostatic R image in the photoconductive layer. Exposing the surfacein 3 5 this manner forms a pattern of electrostatic charge by virtue ofthe fact that light energy striking the photoconductor causes 3, theelectrostatic charge in the light struck areas to be conducted away fromthe surface in proportion to the intensity of where R and R are eacharyl radicals, aliphatic residues of l the illumination in a particulararea. to 12 carbon atoms such as alkyl radicals preferably having l Thrge pa ern produced by exposure is then developed to 4 carbon atoms orhydrogen. Particularly advantageous or transferred to another surfaceand developed there, i.e., results are obtained when R, isa phenylradical including subei h r the charged r h rg areas r n r i i ystituted phenyl radicals and where R is a diphenylaminophentreatmentwith a medium comprising electrostatically responyl, dimethylaminophenylor phenyl. sive toner particles. The developing electrostaticallyrespon- Other photoconductors which can be used with the present siveparticles can be in various forms such as small particles of aggregatecompositions include rhodamine B, malachite p g Or in the fvrm Of Smallparticles c pri ed of a green, crystal violet, phenosafranine, cadmiumsulfide, cadmicolorant in a resinous binder. A preferred method ofapplying um selenide, parachloronil, benzil, trinitrofluoroenone, suchdry toners to a latent electrostatic image for solid areatetranitrofluoroenone,etc. development is by the use of a magneticbrush. Methods of Thg f ll i table 4 comprises a i l li i f U, s,forming and using a magnetic brush toner applicator are Patentsdisclosing a wide variety or organic photoconductive described thefollowing [Palcompounds and compositions which can be improved with 2,72,874,063; 2,984,163; respect to speed, sensitivity, and/or regenerationwhen incorand Reissue 2 ,77 Liquid developporated into the featurecompositions and elements of this inmerit of the latent electroslaucImage can also be usedn vention liquid development the developingparticles are carried to the image-bearing surface in an electricallyinsulating liquid carrier. Methods of development of this type arewidely known and have been described in the patent literature, forexample, U.S. Pat No. 2,907,674 and in Australian Pat. No. 212,315.

In dry developing processes, the most widely used method of obtaining apermanent record is achieved by selecting a developing particle whichhas as one of its components a lowmelting resin. Heating the powderimage then causes the resin to melt or fuse into or on the element. Thepowder is, therefore, caused to adhere permanently to the surface of the1 photoconductive layer. In other cases, a transfer of the electrostaticcharge image formed on the photoconductive layer can be made to a secondsupport such as paper which could then become the final print afterdevelopment and fusing. Techniques of the type indicated are well knownin the art and have been described in a number of U.S. and foreignpatents, such as U.S. Pat. Nos. 2,297,691 and 2,551,582 and in RCAReview Vol. 15 (1954) Pg. 469-484.

Processes such as described hereinbefore have found utility where thephotoconductive layer is either inexpensive and expendable such as thevarious processes using photoconductive zinc oxide, or where thephotoconductive media is rapidly reusable such as vitreous selenium. Thefeature compositions of this invention now permit a large number ofknown organic photoconductive compounds and compositions as well asinorganic materials to be employed in xerographic processes where rapidrepeated charging and exposing are desired. For example, it is nowpossible with the advance provided by the discovery of the compositionsof this invention to employ a closed loop or belt of reusable organicphotoconductive film in a xerographic process thereby permittingextremely rapid reproduction of original images. In addition,photoconductive compositions containing the feature material can, ofcourse, be in the form of coated plates and drums. With the discoverydisclosed herein, it is now possible to reproduce copy from a microfilmor other original as rapidly as the state of the related mechanicalhandling arts will permit.

The following examples are included for a further understanding of theinvention.

Example 1 Coatings of the invention are prepared by dissolving 6 g.poly(4,4'-isopropylidenediphenyl carbonate) resin (a composition formedfrom the reaction between phosgene and a dihydroxydiarylalkane or fromthe ester exchange between diphenylcarbonate and2,2-hydroxphenylpropane, such as Lexan I" polycarbonate resin, GeneralElectric Company); 4 g. of 4,4'-benzylidenebis(N,N-diethyl-m-toluidine)photoconductor; and 0.2 g. of 4-[4-bis(2- chloroethyl)aminophenyl]2,o-diphenylthiapyrylium perchlorate sensitizer in a solventmixture consisting of 85 g. of dichloromethane and 5 g. of methanol bystirring the solids in the solvent for 2 hours at about 70 F; to form asolution. The resulting solution is hand coated at .004-inch wet coatingthickness onto two separate strips of poly(ethylene terephthalate) filmsupport overcoated with a conducting layer containing the sodium salt ofa carboxyester lactone of maleic anhydride and vinyl acetate polymersuch as disclosed in U.S. Pat. No. 3,007,901. The coating block ismaintained at F. during coating. Both coatings are allowed to dry, andonly one of the coatings is taped to a glass plate. This plate isimmediately inverted over a bath of dichloromethane with the coating inthe vapors thereof and kept there in room light at 70 F. for about twominutes. During this vapor treatment, an observable change takes takesplace in the color and general physical appearance of the coating. Thevapor-treated coating and the coating which was not vapor treated areexamined microscopically at SOOX magnification. The vapor-treatedcoating has acquired a granular appearance not present in thenonvapor-treated coating. A spectrophotometric transmission curve forthe vapor-treated coating indicates that the coating absorbed percent ofthe incident radiation at a principal absorption peak of 515 mg. Thecoating which has not been vapor treated absorbs 89 percent at anabsorption peak of 555 mp. It is noted that the absorption peak of thevapor-treated coating has shifted to a shorter wavelength by 40 mpfromthe 555 mp. peak characteristic of the coating which has not been vaportreated. The actual positive electrical speeds of the converted(vapor-treated) and unconverted (nonvapor-treated) coatings aredetermined in the following manner. The element is electrostaticallycharged under a corona source until the surface potential, as measuredby an electrometer probe, reaches about 600 volts. The charged elementis then exposed to a 3,000 K. tungsten light source through atransparent continuous neutral density or gray scale wedge. The exposurecauses reduction of the surface potential of the element under theneutral density wedge from its initial potential, V,,, to some lowerpotential, V, whose exact value depends on the actual amount of exposurein meter-candle-seconds received by the area. The results of thesemeasurements are then plotted on a graph of surface potential V vs. logexposure for each step. The actual positive speed of the element canthen be expressed in terms of the reciprocal of the exposure required toreduce the surface potential to any arbitrarily selected value. Herein,unless otherwise stated, the actual positive speed is the numericalexpression of 10 divided by the exposure in meter-candle-secondsrequired to reduce the 600-volt charged surface potential to a value of100 volts. Measuring as described herein, it is found that the coatingwhich is vapor treated has a speed of 240 when initially chargedpositively. The coating which is not vapor treated has a speed of 63when initially charged positively and a speed of 35 when initiallycharged negatively. The speeds and spectral characteristics of thecoatings described hereinbefore, and similar coatings containing dyesother than 4-[4-bis(2-chloroethyl)aminophenyl1- 2,6-diphenylthiapyryliumperchlorate are tabulated in table 5. All of the converted orheterogeneous coatings can be toned to produce visible images afterbeing charged and image-wise exposed, typical suitable toners beingdisclosed in U.S. Reissue Pat. No. 25,136.

TABLE 5 Converted Unconverted coating heterogeneous coating hmax. 7Percent )tmax. Percent Dye (mu) absorption Speed (my) absorption Speed4-(4-bis (2-ch1oroethyl)-aminophenyl)-2 fi-diphenylthiapyryliumperchlorate (Cmpd. No. 1, Table i). 5 89 i 55 515 I5 i 55,4(4-dirnetl1ylaminophenyl)-2,6-diphenylthiapyrylium fiuoroborate (Cmpd.N0. 3,'Iable1) 585 1 5 mm x 2 54-(4-dimetliylamino-l-methylphenyl)-2,6-dipheny1pyry1ium perchlorate(Cmpd. 4, Table 1).. U 538 so{ 6 452 42{4-(4-dimethylaminopheny1)-2,fi-diphenylthiapyrylium p-toluenesulfonate(Cmpd. 1, Table 1). 570 71 fig 1 680 82 jgg4-(4-dimethylaininopltenyl)-2-(4-mcthoxyphenyl)-6-phenylthiapyry1iumperchloy rate (Cmpd. 11, Table 1) 565 67 i 3; 675 65 't gg4-(4-dimethylanlinopltenyl)-2-(4-ethoxyphenyl)-6-pl1enylthiapyryliumperclilorate (Cmpd. 12, Table 1) 570 71 Q 5 use 153 3 24(4-di1nethy1amhiophenyl)-2,ediphenylthiapyrylium perchlorate (Ompd. 2,Ta b 580 75 j 085 75 j g 1 Minus too slow to measure.

Example 2 The procedure for this example for preparing thephotoconductive coatings is generally the same as described in example 1with the following changes: The sensitizer, 4[4-bis(2-chloroethyl)aminopl1enyl]2,6-diphenylthiapyrylium perchlorate, isreplaced with the same amount of 4-(4-dimethylaminophenyl)-2,o-diphenylthiapyrylium perchlorate (compound No.2, table 1). Two solutions are prepared, one in 90 g. ofdichloromethanesolvent, the other in a solvent mixture consisting of 85 g. ofdichloromethane and 5 g. of methanol. Both solutions are stirred andcoated as in example 1. Upon drying the coating prepared withdichloromethane as the sole solvent is converted into a two phaseheterogeneous material by exposing to the vapors of dichloromethanesolvent TABLE 8 The absorption shift of the two individual dyescontained in the mixtures of the first and third coatings have in effectcombined to give a net absorption peak which is unchanged; however, theabsorption spectrum has changed.

5 Example 4 Converted" llet trogvncous Unconverted coating coatingPolymer abs ofgiz it iii Speed x]: Speed Poly[4,4-isopropy1idenedibenzyl 4,4-isopropy1idene dibenzoate] 585 an i *(530 as l ggdPoly(4,4-isopropylidenediphenyl 4,4-isopropylidene dibenzoate) 580 87 i375 s *Heterogeneous coating formed by vapor treatment overtetrahydrofuran.

as in example 1. A predominant portion of the dye present is Example 5in the particulate discontinuous phase. The coating from the 85 g.dichloromethane, 5 g. methanol solution is not so treated. In additionto the foregoing speed and spectral response changes, another sample ofthe first converted coating shown below is coated on an element having anickel conducting layer and is repeatedly charged to a 600 v. potentialand photodischarged to determine the resistance of the coat ing toelectrical fatigue. After 1,000 such cycles at a time interval of 3seconds between photodischarge and recharging, the coating will accept a550 v. potential under the same charging conditions The uncovertedcoating in the same system will accept only a 400 v. to 450 v.potential. Further cycling produces little change in the ability of theconverted coating to accept a high surface potential while theunconverted coating continues to deteriorate. The speeds and spectralcharacteristics for compositions prepared as described above containingthe same sensitizer binder combination with variations in the organicphotoconductor used are tabulated in table 6.

TABLE 6 An electrophotographic element is prepared by dissolving 9.5 g.of the arylalkane polycarbonate described in example I and 0.5 g. of4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium fluoroboratesensitizer dye in g. of chloromethane solvent by stirring the solids inthe solvent for 2 hours at about 70 F. A second solution is prepared bydissolving 9.5 g. of the polycarbonate and 0.5 g. of4-(4-dimethylaminophenyl)-2.6- diphenylthiapyrylium fluoroborate in asolvent mixture consisting of 66.5 g. dichloromethane and 3.5 g. ofmethanol by stirring the solids in the solvent for 2 hours at about 70 FThe first and second solutions are then separately hand coated at0.005-inch wet coating onto a barrier or insulator overcoated conductinglayer of cuprous iodide coated on a poly(ethylene terephthalate) filmbase. (Conducting layers with or without insulating overcoated barrierlayers of the type used herein are shown in U.S. Pat. No. 3,245,833).The coating block is main tained at 90 F when solutions 1 and 2. arecoated. After dry- 45 ing, the first coating is treated with solventvapor as in example l and each of the coatings is examinedmicroscopically at Unconverted coating Converted heterogeneous coatingmax Percent max. P r t Photooonduotot i flbsflrptlon peed u) absorptionSpeed 4,4'-benzylldenebis(N,N-diethyl-m-toluidine)... 580 i 56 685 75wil w 1,3,6-tripheny12-pyrazoline 595 9a 1 680 81 @586 3; r p y e H 51086 t 79 Example 3 500X magnification. It is noted that the coating fromthe first Photoconductive compositions and elements are prepared by theprocedures of example 1. with the following changes: the sensitizer,4-[4-bis(2-chloroethyl)aminophenyl]-2,6- diphenylthiapyryliumperchlorate, is replaced by the same amount of a mixture of sensitizerdyes in each case. The

solution has a granular appearance not present in the second coating. Inaddition, at least a predominant portion of the dye present in the firstcoating is contained in the granular appear ing discontinuous phase Thespectrophotometric transmis sion curve for the first coating indicatesthat the coating ab sorbs 93 percent of the incident radiation ,at anabsorption speeds and spectral characteristics for compositions contain-65 ing sensitizer mixtures are tabulated in table 7 peak of 640 mp.. Thesecond coating absorbs 94 percent at a TABLE 7 Converted Uneonvertedcoating heterogeneous coating Max. Percent Max. Percent Dye mixture (mabsorption Speed (m absorption Speed 87.5 by weight Cmpd. 1, Table 1....+35; +1, 600; 12.5%, by weight Ompd. 2, Table 1 565 88 i -20 565 81 i1,6oo by Weight Ompd. 1, Table 1 550 82 +32; 510 65 t +1, 400, 15% byweigfit gmpg. T%llalell $4250 I ,2%%0 7 byweig t m a e 1 1072 Cmpd. 7,Tab 0 1.. 85 i -28 6 i -250 peak of 580 mp" It is noted that theabsorption peak of the first coating has shifted to a longer wavelengthby 60 mp, from the 580 my which is characteristic of the second coating.The speeds of these coatings are measured using the procedure describedfor example l. However, in this case, the speed of the coating isdetermined on the basis of the reciprocal of the exposure required toreduce the potential of the surface charge by 100 volts (shoulder speed)as measured with an electrometer probe. It is found that the firstcoating has a speed of 630 when initially charged positively, and 1,200when initially charged negatively. The second coating has low speed wheninitially charged positively or negatively. The

speeds and spectral characteristics of coatings madein this same manner,and which contain dyes other than 4-(4- Example 6 The procedure ofexample 1 is generally repeated using as the sensitizer 0.4 g. of4-(4-dimethylaminophenyl)-2,6- diphenylthiapyrylium perchlorate in placeof the 4-[4,-bis(2- chloroethyl)-aminophenyl]-2,6-diphenylthiapyryliumperchlorate. The polycarbonate resin, the photoconductor and thesensitizer are dissolved in a solvent mixture of 52.5 g. ofdichloromethane and b'52.5 g. of l,2-dichloroethane by stirring thesolids in the solvent for 2 hours at about 70 F. The resulting dope isthen coated onto a conducting substrate and converted into a two phasecomposition in the manner shown in example 1. The substrate consists ofan evaporated nickel film coated on a poly(ethylene terephthalate) filmbase which is subbed with a terpolymer of 2 weight percent itaconicacid, 13 weight percent methyl acrylate and 85 weight percent vinylidenechloride. The net density of the evaporated nickel film is about 0.10and resistivity of the substrate is about ohms/sq. This photoconductivecoating has an absorption peak at 675 mu and absorbs 94 percent of theincident radiation at this wavelength. The positive and negative 3second, 1,000 cycle regeneration of the coating (measured as describedin example 2) is excellent and the positive and negative speeds measuredas in example 1 are 3,200 and 3,500, respectively. The densities andresistivities of other metal conducting substrates as well as the speedsand absorption of other organic photoconductive coatings which arecoated directly on these metal substrates are tabulated in table l0. Thephotoconducting layers show excellent regeneration pro- Example 7 Theprocedure of example I is repeated using as the dye2,6-bis-(4-ethylphenyl)4-(4-dimethylaminophenyl)thiapyrylium perchlorate(Compound 10, table 1). After hand coating the resulting solution, anovercoat of toluene is applied in place of the solvent vapor treatment.Upon drying the feature composition is formed The absorption maximum is570 my (87 percent absorption) for the unconverted coating and 635m;t(93 percent absorption), respectively, for the converted coating.Speeds for the coatings are determined forboth positive and negativecharging. The speeds of the unconverted coating are ++l00 and 56 whereasthe converted coating has speeds of+450 and 500.

Example 8 The procedure of example 1 is repeated using 4-(4-dimethylaminophenyl-Z,6-diphenylthiapyrylium perchlorate as the dye and90 g. of dichloromethane as the solvent. Two coatings are then formed asin example 1 without the subsequent vapor treatment. The first coatingis converted by covering immediately after coating so as to restrict therate of solvent evaporation. The second coating is converted byimmersing briefly in a bath of benzene. After drying, comparisonsbetween converted and unconverted coatings are made. The unconvertedcoating has speeds of +40 and -30, whereas the first converted coatinghas a speed of +2,000 and 2,000, while the second converted coating hasspeeds of +1 ,600 and l ,800.

Example 9 The procedure of example I is repeated using a solvent mixturecontaining a high boiling solvent. The solvent mixture consists of 81 g.of dichloromethane and 9 g. of toluene. The mixture is coated as inexample 1 and allowed to dry at room temperature which results in thesolvent being in contact with the coating long enough to causeconversion to the aggregate. The final converted coating has positiveand negative speeds of l,800 and 2,l00, respectively.

The following two examples demonstrate the improved results obtained byusing a higher viscosity polycarbonate in forming the heterogeneouscompositions of the present invention.

Example 10 Control Coating A 35.3-gram portion ofa low viscosityBisphenol A polycarbonate having an inherent viscosity of about 0.56.23.5 grams of 4,4'-benzylidenebis (N,N-diethyl-m-toluidine, and 1.2grams of 4-(4-dimethylaminophenyl)-2,o-diphenylthiapyrylium perchlorateare dissolved in a solvent mixture comprised of 242 ml. ofdichloromethane and l50 ml. of 1,1,2- trichloroethane by stirring thesolids in the solvent for four hours at room temperature. The resultingsolution is then sheared in a water-jacketed high speed shearing blenderfor 30 minutes in accordance with the procedures described in copendingGramza application, U.S. Ser. No. 674,006, filed Oct. 9, I967. The waterin the jacket of the blender is maintained at 50 F. during shearing. Thesheared dope is then coated at a coverage of l g./ft. on a poly(ethyleneterephthalate) film base carrying a conductive layer ofa sodium salt ofaper i n can be repeatedly chargedmxposed and iofled- 0 polymeric lactoneas described in U.S. Pat. NO. 3,260,706.

TABLE 10 Conducting substrate Organic photoconducting layer DensityResistiv- Max. Percent uh- Speed (100 Metal (net) tty, Q/sq. Composition(m sorption v. tov) Nickel .10 10 Polycarbonate of Examplel/4,4'-l)enzylidenc-bis(N,N-diethyl-m-tolui- H20 .15 ,0l)0;

di11e)(60/40)+4% 4-(4-din1etliylaminoplienyl)-2,G-liphenyltliiapyryliuni -l, 000 fiuoroborate.

Niehrome .05 10 Polycarbonate of Example1/4,4-benzylidene-bis(N,N-tliethyl-m-tolut 085 U +2,500; (Driverdine)(/40) +2% 4(4-(limethylaminopelmyl)2,tl-diplicnyltliiapyryliuni 2,500Harris perchlorate.

Company).

Titaniu 5 106 ycarbonate of Example1/4,4-benzylidene-bls(N,N-diethyl-m-tolui- 685 am +2, 500;

dine) (60/40)+2% 4(4-dimethylaminopllenyl)2,6-diplienyltliiapyryl--2,00U ium perchlorate.

Type 316 .05 10 5 Polycarbonate of Examplel/4,4-benzylldene-bis(N,N-diethyl-rn-tolui G .10 +2,50t);stainlesssteel. dine) (60/40)+2% 4(4-din1uthylaniinophcnyl)2,tldiplicuyltltiapyryI 1,.)00

iurn perchlorate.

The coating is allowed to dry and then examined microscopi cally usingtransmitted light and 450K magnification. it is noted that the coatingis heterogeneous in nature. The spectrophotometric transmissioncharacteristics of the coating are then measured and it is found thatthe coating absorbs 92 percent of incident radiation at 690 mg, 80percent at 600 mpand 20 percent at 500 mg. The electrophotographic speedof the coating is then measured as in the previous examples and thepositive and negative 100-volt toe speeds of the coating are found to be2,500 and 2,850, respectively for this control coating.

High Viscosity Coating A second coating is made using 16.2 grams ofBisphenol A polycarbonate having an inherent viscosity of 2.70 asmeasured in l,2-dichloroethane, 10.8 grams of the above photoconductorand 3 grams of the above thiapyrylium dye. The solids are dissolved in asolvent mixture comprises of 228 ml. of 1,2-dichlorethane and 213 ml. ofdichloromethane by stirring into the solvents for four hours at roomtemperature.

The resulting solution is sheared in a water-jacketed high speedshearing blender as in the control coating while maintaining the watertemperature at 50 F. The sheared dope is coated at a coverage of lg./ft. on a conducting substrate similar to that used in the controlcoating. The coating is allowed to dry and examined microscopicallyusing transmitted light 450x magnification. It is noted that the coatingcontains a very fine grain dense discontinuous phase. This heterogeneouscoating is much finer grained than the control coating above. Thecoating is also examined visually with the unaided eye and it is notedthat the surface of the second coating has very little orange peel ascompared to the control coating. The spectrophotometric transmissioncharacteristics ofthe coating absorbs over 90 percent of the incidentradiation at all wavelengths between 530 m tand 700 mp. Theelectrophotographic speeds of the coating are measured as in theprevious example and it is found that the negative toe speed of thiscoating is three times faster than the negative toe speed of the controlcoating. The positive and negative toe speed of the control coating. Thepositive and negative 100-vo1t toe speeds are 400 and 9,500,respectively. Example 11 Coating A is prepared by dissolving 18 grams ofthe polycarb'onate binder of example 1 in 201 ml. of dichloromethane bystirring the binder in the solvent for two hours at room temperature.The resulting solution is placed in a water-jacketed high speed shearingblender and 12 grams of photoconductive zinc oxide are added to thesolution which thereafter is sheared for ten minutes. The water in thejacket of the blender is maintained at 70 F. during shearing. Thesheared dispersion is hand-coated at a 0.008-inch wet coating thicknesson a poly(ethylene terepthalate) support having a 0.4 neutral densityhigh vacuum evaporated nickel conducting layer thereon.

The coating block is maintained at a temperature of 70 F.

during coating. Next, coating B is prepared by dissolving 17.6 g. of thepolycarbonate binder in 194 ml. of dichloromethane as previously. Theresultant solution is then placed in the jacketed high speed shearingblender with the addition of l 1.8 grams of photoconductive zinc oxideand the mixture is sheared for 10 minutes with the water temperaturebeing maintained at 70 F. After shearing, 0.6 grams of 4-(4-dimethylaminophenyl)-2,G-diphenylthiapyrylium perchlorate and 13 m1. ofmethyl alcohol are simply stirred into the sheared dispersion for 30minutes at room temperature. The resulting dispersion is hand coated ata 0.008-inch wet coating thickness on a nickel-coated support as above.Next, coating C is prepared by dissolving 17.6 grams of the abovepolymer and 0.6 grams of the thiapyrylium dye of coating B in 201 ml. ofdichloromethane by stirring for two hours at room temperature. Theresultant solution is placed in a high speed shearing blender andsheared for 30 minutes after which 11.8 grams of photoconductive zincoxide are added to the blender followed by additional shearing for 5minutes with the water in the jacket of the blender being maintained at70 F. during shear- .2; ing. The sheared dispersion is hand coated aspreviously onto a similar conducting support. The coatings, A, B, and Care dried in a laboratory oven at 60 C. for 16 hours. The electrophotographic speeds and spectral characteristics for each of thethree coatings are determined and are tabulated in table 1 1 below:

Coating A is prepared by dissolving 3.73 grams of Bisphenol Apolycarbonate, 6.07 grams of phenyl-tri(p-diethylaminophenyl)stannane,and 0.2 grams of 4-(4- I drmethylaminophenyl)-2,G-diphenylthiaphyryliumperchlorate in a solvent mixture of 38.3 ml. of

dichloromethane, 23.7 ml. of 1,1,2-trichloroethane, and 5.7 ml. ofmethanol by stirring the solids in the solvent for 2 hours at 20 C. Theresulting solution is hand coated on a nickelcoated subbed poly(ehtyleneterephthalate) support as described in example 6, held at a temperatureof 20 C. Coating B is prepared by dissolving 3.73 grams of Bisphenol Apolycarbonate, 6.07 grams of .phenyl-tri-(pdiethylaminophenyl)stannaneand 0.2 grams of 4-(4- dimethylaminophenyl)-2,o-diphenylthiapyryliumperchlorate in a solvent mixture identical to that used for preparingCoating A. Stirring is carried out in the same manner as above, afterwhich the solution is placed in a water-jacketed high speed shearingblender while 20 C. water is circulated through the jacket. The shearedsolution is then coated and dried in the same manner as is done forCoating A. Coatings A and B are dried in a laboratory oven held at 60 C.for 16 hours. The electrophotographic speeds and spectralcharacteristics are determined as in the above examples and the valuesare shown in table 12 below.

TABLE 12 Speed Positive Negative Max. Percent V0 100 v. V0 100 v.Coating (mp) absorption (volts) toe (volts) toe Example 13 An 8 g.portion of the binder of example 1 and 2 g. of 2,4,7-trinitro-9-fluorenone are dissolved in 67 ml. of dichloromethane bystirring the solids in the solvent for 2 hours at room temperature. Theresulting solution is hand coated at an 0.006-inch wet coating thicknesson 0.4 neutral density subbed evaporated nickel substrate. The coatingblock is maintained at 70 F. during coating. A second coating isprepared by dissolving 7.85 g. of the above binder, 1.96 g. of2,3,7-trinitro-9-fluorenone, and 0.2 g. of 4-(4-dimethylamonophenyl)-2,G-diphenylthiapyrylium perchlorate in a solventmixture consisting of 63.8 ml. of dichloromethane and 5.7 ml. of methylalcohol by stirring the solids in the solvent for 2 hours at roomtemperature. The resulting solution is hand coated at an 0.006-inch wetcoating thickness on a poly(ethylene terephthalate) film base carrying aconducting trichloroethane by stirring the solids in the solvent for 2hours at room temperature. The resulting solution is placed i in ajacketed, high-speed shearing blender and sheared for 30 minutes. Thewater in the jacket of the blender is maintained at 70 F. whileshearing. The sheared material is hand coated as above. The coatings l,2, and 3 are dried in a laboratory oven at 60 C. for 16 hours. The 100V. toe speeds and spectral characteristics are determined for each ofthe coatings as in the previous examples and the values are tabulated intable 13.

TABLE 13 Speed Positive Negative AMax Percent Va 100 v. V 100 v. Coating(mu) absorption (volts) toe (volts) too 1 Unsensltized. 2 Too slow to bemeasured.

Example l4 A control coating is prepared by dissolving 0.375 g. of 4-(4-dimethylaminophenyl) 2,o-diphenylthiapyrylium fluoroborate, 4.5 g.poly(4,4-isopropylenediphenylcarbonate-block-oxytetramethylene) and 3 g.of 4,4'-benzylidenebis(N,N-diethylmtoluidine 42.5 g. of methylenechloride. The solution is coated on a conducting support as in thepreceding example. Next, a similar solution is prepared followed byshearing in a water-jacketed high-speed shearing blender for 30 minutesduring which time the water in the jacket is maintained at 70 F. Thesheared composition is coated as above to form a second element. Theabsorption maximum for the control coating is at 585 mu; whereas, themaximum for the converted second coating is at 690 my The resultantsecond element can be charged imagewise, exposed and developed as inexample 1 to form a visible image.

tion that the compositions of the present invention can be used inelectrophotographic elements having many structural variations. Forexample, the photoconductive composition can be coated in the form ofsingle layers or multiple layers on a suitable opaque or transparentconducting support.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

I claim:

1. A heterogeneous photoconductive composition comprising anelectrically insulating polymeric material having an alkylidenediarylene moiety in the recurring unit, a pyrylium dye which has beensolubilized with said polymeric material and a photoconductor, saidcomposition being in the form of a multiphase organic solid comprising acontinuous phase of said polymeric material having therein a particulatediscontinuous phase containing a combination ofsaid dye and saidpolymeric material, the individual portions of said discontinuous phasehaving a size of about 0.01 to 25 microns, said composition having amaximum radiation absorption at a wavelength at least about my.different from the wavelength of maximum absorption of said dyesolubilized with said polymeric material in a homogenous composition.

2. The composition as described in claim 1 wherein said dye is selectedfrom the group consisting of a thiapyrylium dye salt, a selenapyryliumdye salt and a pyrylium dye salt.

3. The composition as described in claim 1 wherein said iri sulatingpolymeric material is selected from the group consisting of carbonatepolymers having an alkylidene diarylene moiety in the recurring unit,poly(4,4'-isopropylidenedibenzyl-4,4'-isopropylidene dibenzoate) andpoly(4,4'- isopropylidene dibenzyl-4,4-isopropylidene dibenzoate).

4. A composition as described in claim 1 wherein said dye is selectedfrom the group consisting of perchlorate, fluoroborate andp-toluenesulfonate salts of 4-[4-bis(2-chloroethyl)aminophenyl]2,6-diphenylthiapyrylium.

5. A composition as described in claim I wherein said dye is selectedfrom the group consisting of perchlorate, fluoroborate andp-toluenesulfonate salts of 4-(4-dimethylamino-phenyl)-2,o-diphenylthiapyrylium,

6. A composition as described in claim 1 wherein said dye is selectedfrom the group consisting of perchlorate, fluoroborate andp-toluenesulfonate salts of2,6-bis(4-ethylphenyl)-4-(4-dimethylaminophenyl)thiapyrylium.

7. A composition as described in claim 1 wherein said dye is selectedfrom the group consisting of perchlorate, fluoroborate andp-toluenesulfonate salts of 4-(4-dimethylamino-phenyl)-2-(4-ethoxyphenyl)-6-phenylthiapyrylium.

8. A composition as described in claim I wherein said dye is selectedfrom the group consisting of perchlorate, fluoroborate andp-toluenesulfonate salts of an anion selected from the group consistingof 4-(4-dimethylamino-2- methylphenyl)-2,6-diphenylpyrylium, 4-[4-di(2-.A 30 chloroethyl)aminophenyl]2-(4-methoxyphenyl)-6-phenylthiapyrylium,4-(4-dimethylaminophenyl)-2,6-diphenylthiaprylium,4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium,2-(2,4-dimethoxyphenyl)-4(4-dimethylaminophenyl)benzo(b)pyrylium,and 4-4-dimethylaminophenyl)-2-(4- methoxyphenyl)-6-phenylthiapyrylium.

9. A heterogeneous photoconductive composition containing a dye selectedfrom the group consisting of pyrylium, thiapyrylium and selenapyryliumdye salts and a hydrophobic carbonate polymer having an alkylidenediarylene moiety in a recurring unit, said dye having been solubilizedwith said polymer, said composition being in the form of a multiphaseorganic solid comprising a continuous binder phase of said polymerhaving dispersed therein a particulate discontinuous phase comprising acombination of said dye and said polymer, the individual portions ofsaid discontinuous phase having a size of about 0.01 to 25 microns, saidcomposition having a maximum radiation absorption at a wavelength atleast about 10 m different from the wavelength of maximum absorption ofsaid dye solubilized with said carbonate polymer in a homogeneouscomposition.

10. A composition as described in claim 9 wherein the pyrylium dye hasthe formula:

wherein:

R and R, are aryl radicals selected from the group consisting of phenyland substituted phenyl having at least one substituent selected from thegroup consisting of an alkyl radical of from i to 6 carbon atoms and analkoxy radical of from 1 to 6 carbon atoms;

R; is an alkylamino-substituted phenyl radical having from 1 to 6 carbonatoms in the alkyl moiety;

X is selected from the group consisting of sulfur and oxygen;

and

Z'is an anion:

and wherein the hydrophobic polymeric material is a filmforming polymercontaining the following recurring unit:

wherein:

R is a phenylene radical and each of R., and R when taken separately, isselected from the group consisting of a hydrogen atom, alkyl radical offrom I to 10 carbon atoms and a phenyl radical and Rj and R when takentogether, are the carbon atoms neces sary to form a cyclic hydrocarbonradical, the total number ofcarbon atoms in R and R being up to 19.

11. An electrophotographic element comprising an electrically conductivesupport having thereon at least one heterogeneous photoconductivecomposition comprising an electrically insulating polymeric materialhaving an alkylidene diarylene moiety in the recurring unit, a pyryliumdye which has been solubilized with said polymeric material and aphotoconductor, said composition being in the form ofa multiphaseorganic solid comprising a continuous phase of said polymeric materialhaving therein a particulate discontinuous phase containing acombination of said dye and said polymeric material, the individualportions of said discontinuous phase having a size of about 0.01 to 25microns, said composition, when bearing an electrostatic charge on asurface thereof, being capable of losing the charge in proportion to theintensity of incident light striking said surface of the composition,the light energy in meter-candle-seconds incident said surface capableof causing a IOO-volt reduction in said charge is not more than 200meter-candle-seconds and said composition being characterized by anability to absorb radiation in a wavelength range different from thewavelength range for a homogeneous composition containing said dyesolubilized with said polymeric material.

12. Anelement as described in claim 11 wherein the composition containsan organic photoconductor different from said dye.

13. An element as described in claim 12, wherein said photoconductor is4,4-benzylidenebis(N,N-diethyl-mtoluidine), said dye being present in anamount of from about 0.001 to about 30 percent by weight of saidcomposition and said dye being selected from the group consisting of4-(4-bis(2 -chloroethy1)aminophenyl]-2,6-diphenylthiapyryliumperchlorate; 4-(4-dimethylaminophenyl-2,-diphenylthiapyryliumperchlorate; 4-(4-dimethylaminophenyl-2,6-diphenylthiapyryliumfluoroborate; 4-(4-dimethylamino-2- methylphenyl)2,6-diphenylpyryliumperchlorate; 4-(4- dimethyl-aminophenyl)-2,6-diphenylthiapyryliumptoluenesulfonate; 4-(4dimethylaminophenyl)-2-(4-methoxyphenyl)-6-phenylthiapyrylium perchlorate and 4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenylthiapyryliumperchlorate.

14. A method for forming a composition which is capable of responding todifferences in light intensity by exhibiting a dif ferentialconductivity when disposed to receive modulated electromagneticradiation comprising the steps of solubilizing a pyrylium dye with ahydrophobic carbonate polymer having an alkylidene diarylene moiety in arecurring unit, coating a layer of the solubilized dye and polymer on asupport, subjecting the layer to solvent for said dye and polymerwhereby a heterogeneous two-phase material is formed in situ in saidlayer, said two phases being visible under 2500X magnification, thecontinuous organic binder phase of said carbonate polymer havingdispersed therein a discontinuous phase of said material containing asignificant portion of said dye in combination with said polymer andsaid material having a maximum radiation absorption at a wavelength atleast about l mudifferent from the wavelength of maximum absorptionofsaid dye solubilized with said polymer.

15. The method of claim 14, wherein the solvent used is a halogenatedhydrocarbon solvent.

16. The method of claim 14 wherein the coated layer is subjected to thesolvent in vapor form for a time sufficient to form the heterogeneoustwo-phase material.

17. The method of claim 14 wherein the coated layer is subjected to thesolvent by overcoating with the solvent in liquid form for a timesufficient to form the heterogeneous twophase material.

18. A heterogeneous photoconductive composition containing anelectrically insulating polymeric material having an alkylidenediarylene moiety in the recurring unit and a pyrylium dye which has beensolubilized with said polymeric material, said composition being in theform of a multiphase organic solid comprising a continuous binder phaseof said polymeric material having dispersed therein a particulatediscontinuous phase comprising a combination of said dye and saidpolymeric material, the individual portions of said discontinuous phasehaving a size of about 0.01 to 25 microns, said composition having amaximum radiation absorption at a wavelength at least about mp differentfrom the wavelength of maximum absorption of said dye solubilized withsaid polymeric material in a homogeneous composition.

19. A composition as described in claim 18 wherein the pyrylium dye hasthe formula:

wherein:

R and R are aryl radicals selected from the group consisting of phenyland substituted phenyl having at least one substituent selected from thegroup consisting of an alkyl radical of from 1 to 6 carbon atoms and analkoxy radical of from 1 to 6 carbon atoms;

R is an alkylamino-substituted phenyl radical having from 1 to 6 carbonatoms in the alkyl moiety;

X is selected from the group consisting of sulfur and oxygen;

and

Z'is an anion;

and wherein the polymeric material is a film-forming polymer containingthe following moiety in a recurring unit:

R11 R; R7 Qs M.

it. w

wherein:

each of R and R when taken separately, is selected from the groupconsisting of a hydrogen atom, an alkyl radical of from 1 to 10 carbonatoms and a phenyl radical, and R and R when taken together, are thecarbon atoms necessary to form a cyclic hydrocarbon radical, the totalof carbon atoms in R and R being up to 19;

R and R are each selected from the group consisting of hydrogen, alkylradicals of from I to 5 carbon atoms, alkogry radicals of from 1 to 5carbon atoms and a halogen; an

R is selected From the group consisting of divalent radicals having theformulas:

said composition comprising a combination of said dye and carbonatepolymer, the individual portions of said discontinuous phase having asize of about 0.01 to about 25 microns, and said composition having aradiation wavelength range of absorption different from the wavelengthrange of absorption of a homogeneous composition comprised of said dyesolubilized in said polymer, said heterogeneous composition when bearingan electrostatic charge on a surface thereof being capable of losingsaid electrostatic charge in proportion to the intensity of incidentactinic radiation such that the incident radiation energy inmeter-candle-seconds required to cause a l-volt reduction in the chargeis not greater than about 200 metercandle-seconds.

21. An electrophotographic element as described in claim 20 wherein saidcarbonate polymer has an inherent viscosity no greater than about I.

22. In an electrophotographic process wherein an electrostatic chargepattern is formed on a photoconductive element, the improvement whereinsaid element has a photoconductive layer comprising an organicphotoconductor in a heterogeneous composition comprising an electricallyinsulating polymeric material having an alkylidene diarylene moiety in arecurring unit and a pyrylium dye which has been solubilized with saidpolymer material, said composition being in the form of a multiphaseorganic solid comprising a continuous phase of said polymer materialhaving therein a particulate discontinuous phase containing acombination of said dye and said polymer material, the individualportions of said discontinuous phase having a size of about 0.01 to 25microns, said composition having a maximum radiation absorption at leastabout [0 mp. different from the wavelength of maximum absorption of saiddye solubilized with said polymeric material in a homogeneouscomposition.

imum of said dye solubilized with said polycarbonate.

24. An electrophotographic element comprising a conductive supporthaving thereon a layer of a heterogeneous photoconductive compositioncomprising a continuous organic binder phase having dispersed therein adiscontinuous phase comprising an organic photoconductor sensitized witha particulate combination of a carbonate polymer having an alkylidenediarylene moiety in a recurring unit and a thiapyrylium dye salt, saiddye salt having been solubilized with said carbonate polymer, saidparticulate combination having a size of about 0.01 to 25p, and saidcombination having a wavelength of maximum radiation absorption which isat least l0m different from the radiation absorption maximum of said dyedissolved with said carbonate polymer in a homogeneous composition.

25. An electrophotographic element as described in claim 24 wherein saiddye salt is selected from the group consisting of fluoroborate andperchlorate salts of 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyryliumand 4-(4- dimethylamino-phenyl)-2- (4-ethoxyphenyl-6-phenylthiapyrylium.

26. An electrophotographic element as described in claim 24 wherein saidcarbonate polymer is poly(4,4'-isopropylidenediphenylene carbonate).

2. The composition as described in claim 1 wherein said dye is selectedfrom the group consisting of a thiapyrylium dye salt, a selenapyryliumdye salt and a pyrylium dye salt.
 3. The composition as described inclaim 1 wherein said insulating polymeric material is selected from thegroup consisting of carbonate polymers having an alkylidene diarylenemoiety in the recurring unit, poly(4,4-isopropylidene-dibenzyl-4,4''-isopropylidene dibenzoate) and poly(4,4''-isopropylidenedibenzyl-4,4''-isopropylidene dibenzoate).
 4. A composition as describedin claim 1 wherein said dye is selected from the group consisting ofperchlorate, fluoroborate and p-toluenesulfonate salts of4-(4-bis(2-chloroethyl)aminophenyl)-2,6-diphenylthiapyrylium.
 5. Acomposition as described in claim 1 wherein said dye is selected fromthe group consisting of perchlorate, fluoroborate and p-toluenesulfonatesalts of 4-(4-dimethylamino-phenyl)-2,6-diphenylthiapyrylium,
 6. Acomposition as described in claim 1 wherein said dye is selected fromthe group consisting of perchlorate, fluoroborate and p-toluenesulfonatesalts of 2,6-bis(4-ethyl-phenyl)-4-(4-dimethylaminophenyl)thiapyrylium.7. A composition as described in claim 1 wherein said dye is selectedfrom the group consisting of perchlorate, fluoroborate andp-toluenesulfonate salts of4-(4-dimethylamino-phenyl)-2-(4-ethoxyphenyl)-6-phenylthiapyrylium.
 8. Acomposition as described in claim 1 wherein said dye is selected fromthe group consisting of perchlorate, fluoroborate and p-toluenesulfonatesalts of an anion selected from the group consisting of4-(4-dimethylamino-2-methylphenyl)-2,6-diphenylpyrylium,4-(4-di(2-chloroethyl)aminophenyl)-2-(4-methoxyphenyl)-6-phenylthiapyrylium,4-(4-dimeThylaminophenyl)-2,6-diphenyl-thiaprylium,4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium,2-(2,4-dimethoxyphenyl)-4-(4-dimethylaminophenyl)benzo(b)pyrylium,and 4-4-dimethylaminophenyl)-2-(4-methoxyphenyl)-6-phenylthiapyrylium.9. A heterogeneous photoconductive composition containing a dye selectedfrom the group consisting of pyrylium, thiapyrylium and selenapyryliumdye salts and a hydrophobic carbonate polymer having an alkylidenediarylene moiety in a recurring unit, said dye having been solubilizedwith said polymer, said composition being in the form of a multiphaseorganic solid comprising a continuous binder phase of said polymerhaving dispersed therein a particulate discontinuous phase comprising acombination of said dye and said polymer, the individual portions ofsaid discontinuous phase having a size of about 0.01 to 25 microns, saidcomposition having a maximum radiation absorption at a wavelength atleast about 10 m Mu different from the wavelength of maximum absorptionof said dye solubilized with said carbonate polymer in a homogeneouscomposition.
 10. A composition as described in claim 9 wherein thepyrylium dye has the formula: wherein: R1 and R2 are aryl radicalsselected from the group consisting of phenyl and substituted phenylhaving at least one substituent selected from the group consisting of analkyl radical of from 1 to 6 carbon atoms and an alkoxy radical of from1 to 6 carbon atoms; R3 is an alkylamino-substituted phenyl radicalhaving from 1 to 6 carbon atoms in the alkyl moiety; X is selected fromthe group consisting of sulfur and oxygen; and Z is an anion: andwherein the hydrophobic polymeric material is a film-forming polymercontaining the following recurring unit: wherein: R is a phenyleneradical and each of R4 and R5, when taken separately, is selected fromthe group consisting of a hydrogen atom, alkyl radical of from 1 to 10carbon atoms and a phenyl radical and Rj4 and R5, when taken together,are the carbon atoms necessary to form a cyclic hydrocarbon radical, thetotal number of carbon atoms in R4 and R5 being up to
 19. 11. Anelectrophotographic element comprising an electrically conductivesupport having thereon at least one heterogeneous photoconductivecomposition comprising an electrically insulating polymeric materialhaving an alkylidene diarylene moiety in the recurring unit, a pyryliumdye which has been solubilized with said polymeric material and aphotoconductor, said composition being in the form of a multiphaseorganic solid comprising a continuous phase of said polymeric materialhaving therein a particulate discontinuous phase containing acombination of said dye and said polymeric material, the individualportions of said discontinuous phase having a size of about 0.01 to 25microns, said composition, when bearing an electrostatic charge on asurface thereof, being capable of losing the charge in proportion to theintensity of incident light striking said surface of the composition,the light energy in meter-candle-seconds incident said surface capableof causing a 100-volt reduction in said charge is not more than 200meter-candle-seconds and said composition being characterized by anability to absorb radiation in a wavelength range different from thewavelength range for a homogeneous composition containing said dyesolubilized with said polymeric material.
 12. An element as described inclaim 11 wherein the composition contains an organic photoconductordifferent from said dye.
 13. An element as described in claim 12,wherein said photoconductor is4,4''-benzylidenebis(N,N-diethyl-m-toluidine), said dye being preseNt inan amount of from about 0.001 to about 30 percent by weight of saidcomposition and said dye being selected from the group consisting of4-(4-bis(2-chloroethyl)aminophenyl)-2,6-diphenylthiapyryliumperchlorate; 4-(4-dimethylaminophenyl-2,6-diphenylthiapyryliumperchlorate; 4-(4-dimethylaminophenyl-2,6-diphenylthiapyryliumfluoroborate; 4-(4-dimethylamino-2-methylphenyl)2,6-diphenylpyryliumperchlorate; 4-(4-dimethyl-aminophenyl)-2,6-diphenylthiapyryliump-toluenesulfonate; 4-(4-dimethylaminophenyl)-2-(4-methoxyphenyl)-6-phenylthiapyrylium perchlorate and4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenylthiapyryliumperchlorate.
 14. A method for forming a composition which is capable ofresponding to differences in light intensity by exhibiting adifferential conductivity when disposed to receive modulatedelectromagnetic radiation comprising the steps of solubilizing apyrylium dye with a hydrophobic carbonate polymer having an alkylidenediarylene moiety in a recurring unit, coating a layer of the solubilizeddye and polymer on a support, subjecting the layer to solvent for saiddye and polymer whereby a heterogeneous two-phase material is formed insitu in said layer, said two phases being visible under 2500Xmagnification, the continuous organic binder phase of said carbonatepolymer having dispersed therein a discontinuous phase of said materialcontaining a significant portion of said dye in combination with saidpolymer and said material having a maximum radiation absorption at awavelength at least about 10 m Mu different from the wavelength ofmaximum absorption of said dye solubilized with said polymer.
 15. Themethod of claim 14, wherein the solvent used is a halogenatedhydrocarbon solvent.
 16. The method of claim 14 wherein the coated layeris subjected to the solvent in vapor form for a time sufficient to formthe heterogeneous two-phase material.
 17. The method of claim 14 whereinthe coated layer is subjected to the solvent by overcoating with thesolvent in liquid form for a time sufficient to form the heterogeneoustwo-phase material.
 18. A heterogeneous photoconductive compositioncontaining an electrically insulating polymeric material having analkylidene diarylene moiety in the recurring unit and a pyrylium dyewhich has been solubilized with said polymeric material, saidcomposition being in the form of a multiphase organic solid comprising acontinuous binder phase of said polymeric material having dispersedtherein a particulate discontinuous phase comprising a combination ofsaid dye and said polymeric material, the individual portions of saiddiscontinuous phase having a size of about 0.01 to 25 microns, saidcomposition having a maximum radiation absorption at a wavelength atleast about 10 m Mu different from the wavelength of maximum absorptionof said dye solubilized with said polymeric material in a homogeneouscomposition.
 19. A composition as described in claim 18 wherein thepyrylium dye has the formula: wherein: R1 and R2 are aryl radicalsselected from the group consisting of phenyl and substituted phenylhaving at least one substituent selected from the group consisting of analkyl radical of from 1 to 6 carbon atoms and an alkoxy radical of from1 to 6 carbon atoms; R3 is an alkylamino-substituted phenyl radicalhaving from 1 to 6 carbon atoms in the alkyl moiety; X is selected fromthe group consisting of sulfur and oxygen; and Z is an anion; andwherein the polymeric material is a film-forming polymer containing thefollowing moiety in a recurring unit: wherein: each of R4 and R5, whentaken separately, iS selected from the group consisting of a hydrogenatom, an alkyl radical of from 1 to 10 carbon atoms and a phenylradical, and R4 and R5, when taken together, are the carbon atomsnecessary to form a cyclic hydrocarbon radical, the total of carbonatoms in R4 and R5 being up to 19; R6 and R7 are each selected from thegroup consisting of hydrogen, alkyl radicals of from 1 to 5 carbonatoms, alkoxy radicals of from 1 to 5 carbon atoms and a halogen; and R8is selected From the group consisting of divalent radicals having theformulas:
 20. An electrophotographic element comprising a conductivesupport having coated thereon a heterogeneous photoconductivecomposition comprising a polyarylalkane photoconductor, a carbonatepolymer having an alkylidene diarylene moiety in a recurring unit and anorganic dye selected from the group consisting of a pyrylium dye saltand a thiapyrylium dye salt which has been solubilized with saidpolymer, the continuous organic binder phase of said carbonate polymerhaving dispersed therein; a discontinuous phase of said compositioncomprising a combination of said dye and carbonate polymer, theindividual portions of said discontinuous phase having a size of about0.01 to about 25 microns, and said composition having a radiationwavelength range of absorption different from the wavelength range ofabsorption of a homogeneous composition comprised of said dyesolubilized in said polymer, said heterogeneous composition when bearingan electrostatic charge on a surface thereof being capable of losingsaid electrostatic charge in proportion to the intensity of incidentactinic radiation such that the incident radiation energy inmeter-candle-seconds required to cause a 100-volt reduction in thecharge is not greater than about 200 meter-candle-seconds.
 21. Anelectrophotographic element as described in claim 20 wherein saidcarbonate polymer has an inherent viscosity no greater than about
 1. 22.In an electrophotographic process wherein an electrostatic chargepattern is formed on a photoconductive element, the improvement whereinsaid element has a photoconductive layer comprising an organicphotoconductor in a heterogeneous composition comprising an electricallyinsulating polymeric material having an alkylidene diarylene moiety in arecurring unit and a pyrylium dye which has been solubilized with saidpolymer material, said composition being in the form of a multiphaseorganic solid comprising a continuous phase of said polymer materialhaving therein a particulate discontinuous phase containing acombination of said dye and said polymer material, the individualportions of said discontinuous phase having a size of about 0.01 to 25microns, said composition having a maximum radiation absorption at leastabout 10 m Mu different from the wavelength of maximum absorption ofsaid dye solubilized with said polymeric material in a homogeneouscomposition.
 23. A heterogeneous photoconductive composition comprisinga continuous organic binder phase having dispersed thereinphotoconductive zinc oxide sensitized with a particulate combination ofa hydrophobic polycarbonate having an alkylidene diarylene moiety in arecurring unit and a pyrylium dye selected from the group consisting ofa thiapyrylium, a pyrylium and a selenapyrylium salt, said dye havingbeen solubilized with said polycarbonate, said particulate combinationhaving a size of about 0.01 to 25 microns, and said sensitizer having awavelength of maximum radiation absorption which is at least 10 m Mudifferent from the radiation absorption maximum of said dye solubilizedwith said polycarbonate.
 24. An electrophotographic element comprising aconductive support having thereon a layer of a heterogeneousphotoconductive composition comprising a continuous organic binder phasehaving dispersed theRein a discontinuous phase comprising an organicphotoconductor sensitized with a particulate combination of a carbonatepolymer having an alkylidene diarylene moiety in a recurring unit and athiapyrylium dye salt, said dye salt having been solubilized with saidcarbonate polymer, said particulate combination having a size of about0.01 to 25 Mu , and said combination having a wavelength of maximumradiation absorption which is at least 10m Mu different from theradiation absorption maximum of said dye dissolved with said carbonatepolymer in a homogeneous composition.
 25. An electrophotographic elementas described in claim 24 wherein said dye salt is selected from thegroup consisting of fluoroborate and perchlorate salts of4-(4-dimethyl-aminophenyl)-2,6-diphenylthiapyrylium and4-(4-dimethylamino-phenyl)-2- (4-ethoxyphenyl-6-phenylthiapyrylium. 26.An electrophotographic element as described in claim 24 wherein saidcarbonate polymer is poly(4,4''-isopropylidenediphenylene carbonate).